The invention relates to a fuel injector arrangement for supplying fuel into a cylinder of an internal combustion engine. The fuel injector arrangement is configured to be inserted into an opening in a housing part to form a part of a fuel injection system. Said fuel injector arrangement or said fuel injection system may be used in an internal combustion engine, such as a diesel engine, where said engine can be used in any vehicle; such as a truck, bus, construction equipment or stationary power units such as genset etc.
Fuel injectors are used to supply fuel into the cylinders of an internal combustion engine. According to one engine concept example, a fuel distribution channel (a fuel gallery) is arranged crosswise through a housing for feeding fuel to a plurality of fuel injectors. Each fuel injector comprises an internal fuel channel arrangement extending between an opening into the fuel gallery and an opening in an injector tip forming a spray tip. The injection timing may be controlled mechanically and/or electronically for example via a plunger in the fuel injector.
When fuel is injected into a combustion chamber of a cylinder, the combustion of said fuel results in a high gas pressure, which pressure exerts a force on the injector tip and all the way up to a contact area between the fuel injector and an injector sleeve and/or a housing part receiving the injector. The contact area between the fuel injector and the injector sleeve/housing part is established and maintained by the clamping force of an injector yoke which counteracts the force caused by the gas pressure.
Combustion gas seals for injectors have been proposed in US 2003/0178784 A, wherein said seal is attached in an attachment groove provided in the injector, which is to be mounted on a cylinder head of an engine, to seal an annular gap between the cylinder head and the injector. Said seal has an inner diameter which prior to compressive deformation is set to be smaller than an outer diameter of the attachment groove and an outer diameter prior to compressive deformation is set to be larger than an inner diameter of a seal abutment of the cylinder head. An entire end surface of the seal on a combustion gas side is arranged to be exposed to combustion gas. With such constitution, inner and outer diameter sides of the seal are brought into contact with an injector and a cylinder head, respectively, without any gap therebetween, and an entire end surface of the seal is exposed to the combustion gas, so that the seal is caused by pressure applied by the combustion gas to extend toward inner and outer diameter sides, and surface pressures are further increased. The seal is configured and arranged to achieve as good sealing effect as possible.
It is important to maintain a high contact pressure in the contact area between the fuel injector and a cylinder head/an injector sleeve to avoid major leakage of combustion gases past the contact area. Such leakage may result in a pressure building in a cavity between the contact area and the seal which in the end may result in a force reducing the sealing force. The reduced sealing force may result in a severe leakage, which in turn may lead to a contaminated fuel in the fuel gallery.
Even though there may be a high contact pressure at the contact area, micro leakage of the combustion gas may occur and these small micro leakages may in time build a high pressure in the cavity between, the contact area and the seal which may result in reduced sealing force and combustion gases in large amounts entering the fuel system. The combustion gases will carry a high amount of small particles with them and these will contaminate the fuel. Excessive contamination of diesel fuel can cause premature clogging of diesel fuel filters and/or premature wear of critical fuel injection system parts. In addition the combustion gas in the fuel can lead to rough running of the engine as well as engine start issues.
It is desirable to provide a fuel injector arrangement, which creates conditions for a controlled, small leakage of combustion gases passed a seal in order to avoid an uncontrolled pressure build-up of combustion gases on an injector tip side of the seal.
A fuel injector arrangement according to an aspect of the invention comprises a fuel injector and a sealing ring which is arranged around the circumference of the fuel injector. The sealing ring is located between a fuel inlet and/or outlet of the fuel injector located nearest to an injector tip of the fuel injector and the injector tip. Said sealing ring has an asymmetrical cross section with a narrow end extending towards the injector tip and a wider end extending away from the injector tip wherein the wider end edge has a recess therein creating two legs with a space there between.
Proper dimensioning and design of this type of seal creates conditions for a small or more specifically microscopic leakage in the direction from the injector tip to the fuel inlet/outlet. Thus, it secures relief of any pressure build-up on the injector tip side of the seal.
As already mentioned, the fuel gallery connects a plurality of fuel injectors. More specifically, the fuel gallery forms a channel, which connects the openings in the housing for the fuel injectors. A portion of the opening receiving the fuel injector, which portion forms a part of the fuel gallery, may have an enlarged diameter. The opening portion forming the fuel gallery preferably has an extension in an axial direction of the fuel injector which is substantially longer than an extension of said fuel inlet and/or outlet. Preferably, the fuel inlet and/or outlet is positioned within the fuel gallery.
The specific design of the sealing ring allows for a tight seal between the fuel injector and the housing surrounding it when the engine is running. When the engine is running the pressure in the fuel gallery can vary from between 0-40 bar, most often it lies around 5 bar. Once the engine is turned off the pressure in the fuel gallery will slowly diminish and return to 0 bar. In a cavity below the sealing ring, between the fuel injector and the housing, pressure will build up when the engine is running, this pressure will normally lie somewhere between 0-5 bar. Once the engine is turned off and the pressure in the fuel gallery diminishes, the pressure built up in the cavity during the running of the engine will exert a force onto the seal from below whereby the recess in the seal will allow a minute movement of the second leg of the sealing ring towards the first leg and thus a micro leakage is obtained which slowly releases the combustion gas from the cavity into the fuel gallery situated above the sealing ring. The micro leakage of combustion gases from the cavity into the fuel gallery is in the order of 0.001-0.05 ml/hour.
As the pressure in the cavity is released every time the engine is turned off, very low amounts of combustion gas will be released into the fuel on each occasion. These low amounts of combustion gas will not affect the quality of the fuel and thus problems such as rough running of the engine as well as engine start issues can be avoided.
In addition, the construction of the seal allows for a slow release of the combustion gas from the cavity into the fuel gallery which enables the seal to act as a barrier and thereby stop contaminant particles from entering the fuel gallery together with the combustion gas. Hence, the seal will also ensure that the stringent cleanliness requirements of the fuel system are fulfilled.
According to one embodiment the legs of the sealing ring extend in a diverging configuration in a direction from the narrow end towards the wider end. This configuration will allow the sealing ring to increase its flexibility and also allow the possibility of producing a wider seal if such is needed for the specific application. In addition it has also been found that the sealing ring will adjust in guiding the fuel injector when this is positioned into the housing thereby assisting correct placement of the fuel injector.
According to one embodiment a first leg of said legs comprises a substantially straight radially inner surface contacting a radially outer surface of the fuel injector. An advantage of the straight radially inner surface is that the contact between the sealing ring and the fuel injector is improved so that no leakage of combustion gases can occur on this side of the sealing ring.
According to one embodiment the first leg has an at least partly substantially straight extension direction between the narrow end and the wider end. By having a straight extension of the first leg this will allow the sealing ring to fit correctly into a groove on the outer surface of the fuel injector thereby ensuring a correct positioning of the sealing ring.
According to one embodiment a second leg of said legs comprises a free end configured for radial abutment against a radially inner surface of an injector housing part. When the injector is inserted into a housing, the free end will follow the inner surface of the injector housing. This free end will reduce the sensitivity of the size of the sealing ring in relation to the housing as said free end allows for a certain adjustment as it can adjust the width of the seal to follow the surface of the housing. This will also allow for a certain adaptation of the sealing ring to fill out irregularities on the surface of the housing if such are present.
According to one embodiment the second leg has an at least partly substantially straight extension direction between the narrow end and the wider end. This construction has the advantage that the force exerted by the pressure of the combustion gas will be distributed evenly along the width of the leg. An even distribution of the forces allows for an improved calculation of the force exerted on the sealing ring leg at each specific point and this in turn enables an optimization of the sealing ring construction when considering size and materials. In addition, as the force is distributed evenly along the leg of the sealing ring it is less likely to uncontrollably collapse which would be detrimental for maintaining the high quality standard of the fuel.
According to one embodiment a second leg of said two legs projects from a first end of a first leg of said legs at the narrow end. This embodiment has the advantage that the length of the second leg can be varied quite much, from quite short to very long, to adjust to the size of the gap between the fuel injector and the housing.
According to one embodiment the asymmetrical cross section of the sealing ring is in the shape of a V. This embodiment is considered particularly suitable as it is a stable construction allowing for easy production of the sealing ring while at the same time providing optimized stability and sealing properties.
According to one embodiment a second leg of said two legs projects from a position between a first end at the narrow end and a second end at the wider end of a first leg of said legs. A seal with this configuration is considered extra suitable if the gap between the fuel injector and the housing is very narrow as it can be construed not to build as much width while still remaining structurally stable and securing a strong seal between the fuel injector and the housing. Another advantage of this construction is that the pressure exerted onto the sealing ring from the fuel gallery which act on the second leg will have both a pulling force and a pushing force on the first leg which is in contact with the fuel injector and thereby friction is increased which reduces the occurrence of slipping of the sealing ring even if said sealing ring is not placed in a groove on the surface of the fuel injector.
According to one embodiment the sealing ring is in contact with the fuel injector along the complete height of the sealing ring, from the narrow end to the wide end. This embodiment secures a tight fit of the sealing ring around the fuel injector and thereby no leakage will occur in the contact area between the sealing ring and the fuel injector. In addition a large contact area between the sealing ring and the fuel injector will secure a high friction and thus slipping of the sealing ring is avoided even if the sealing ring is not placed in a groove on the fuel injector.
According to one embodiment the angle (a) between the legs of the sealing ring lies between 25 and 70 degrees. By choosing the angle between these intervals it can be secured that the seal performs optimally in that during running of the engine a tight seal is ensured and then when the engine is turned off a micro leakage occurs. In addition by altering the angle the size of the recess between the legs of the sealing ring can be optimized for the intended use.
According to one embodiment the sealing ring is made of an elastic material. A large advantage of elastic materials is that their retraction forces will ensure that a tight seal is achieved between the sealing ring and the fuel injector. Elastic materials are also flexible and will allow for the micro leakage to occur when the engine is turned off.
According to one embodiment the elastic material is chosen from synthetic rubber and thermoplastic elastomers. Synthetic rubber has the advantage that it is highly elastomeric and can undergo a very high elastic deformation and still return to its initial size. The synthetic rubber will thus allow for a sealing ring to be produced which provides a very strong attachment between the sealing ring and the fuel injector in that the elastic forces of the rubber will ensure an inwardly directed force toward the radial center of the fuel injector. Thermoplastic materials have the advantage that they are easy to mold and thus their use will facilitate production of the sealing ring. In addition they are recyclable which will allow the material to be reused when the sealing ring is replaced by a new sealing ring.
According to one embodiment the synthetic rubber is chosen from butadiene rubber, butyl rubber, chlorosulfonated polyethylene, epichlorohydrin, ethylene propylene rubber, fluoroelastomer, nitrile rubber, perfluoroelastomner, polyacrylate rubber, polychloroprene, polyisoprene, polysulfide rubber, polytertafluoroethylene, sanifluor and silicone rubber. These specific rubbers have the advantage of being suitable as material in a sealing ring while at the same time having such properties that the material quality is not compromised by the chemical environment caused by the fuel and combustion gases.
According to one embodiment the thermoplastic elastomer is chosen from thermoplastic elastomer styrenics, thermoplastic polyolefin, thermoplastic polyurethane, thermoplastic etheresterelastomers copolyesters, thermoplastic polyamide, melt processable rubber and thermoplastic vulcanite. These specific thermoplastic elastomers have the advantage of being suitable as material in a sealing ring while at the same time having such properties that the material quality is not compromised by the chemical environment caused by the fuel and combustion gases.
According to one embodiment the sealing ring has a height of 2 to 5 mm, and a width of 0.25 to 4 mm. The height is measured along the first leg from the narrow end of the sealing ring to the wider end of the sealing ring. The width is measured from the surface of the fuel injector to the extension of the second leg which is situated furthest from the surface of the fuel injector. These dimensions are chosen to provide an optimal size of the sealing ring to secure a tight seal between the fuel injector and the housing. If the seal is too bulky then it will be difficult to insert the fuel injector into the housing and if it is too small the sealing ring will not form a tight seal in the gap between the fuel injector and the housing.
The invention also relates to a fuel injection system for supplying fuel into a cylinder of an internal combustion engine, wherein the fuel injection system comprises a housing part with an opening configured for receiving a fuel injector arrangement wherein a fuel injector arrangement is positioned in the opening. When the fuel injector arrangement is inserted into the housing, the sealing ring will provide the benefit of providing a tight seal during running of the engine and then once the engine is turned off the micro leakage will occur thereby removing the pressure built up below the sealing ring in the cavity between the fuel injector and housing. This embodiment will thus ensure that large volumes of combustion gas and particles do not enter the fuel which will ensure a smooth running of the engine and customer complaints due to rough running of the engine as well as engine start issues can be avoided.
According to one embodiment the opening comprises a widened portion forming a fuel gallery around the fuel injector and that a first sealing ring of said sealing rings is positioned around the fuel injector between the fuel gallery and the injector tip. By placing the sealing ring between the fuel gallery and the injector tip of the fuel injector the optimum performance of the improved sealing system provided by the sealing ring is obtained.
The invention also relates to an internal combustion engine comprising a fuel injector arrangement or a fuel injector system as described above. An engine comprising the above described fuel injector arrangement or fuel injector system will ensure a smooth running of the engine. This will have the advantage not only of fewer customer complaints but also that the wear and tear of the fuel injector, filters and other parts of the engine is reduced as the fuel is not polluted by particles and combustion gases. In addition the combustion engine will probably require less maintenance as the parts of the engine will not clog due to unclean fuel.
The invention also relates to a vehicle comprising an internal combustion engine as described above. As described above the internal combustion engine will greatly profit from the fuel injector assembly or the fuel injector system as it will increase the lifetime of said engine and also reduce the maintenance thereof. This advantage will also be present in vehicles comprising an internal combustion engine as disclosed above.
By the term “fuel inlet and/or outlet” is meant an opening in the fuel injector which allows fuel to either enter into the fuel injector, or it allows fuel to exit from the fuel injector and in some cases the opening can have a dual function in that it allows fluid to both enter into the fuel injector and to exit the fuel injector therethrough.